COMPUTED TOMOGRAPHY

DEFINITIONComputer tomography (CT) is originally known as “Computed Axial Tomography”, also known as Body Section Retenography.

It is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation.

ILLUSTRATION OF A CT SCANNER

HISTORYThe first commercially viable CT scanner was invented in 1972 by Godfrey Newbold Hounsfield in Hayes, England using X-rays.

The first scan was done in 1973, of the brain.

Physicist Allan Cormack also invented a similar machine in the United States.

Both Cormack and Hounsfield were awarded the Nobel Prize in 1979.

When X-rays are irradiated on the human body, some of the rays are absorbed and some pass through the body to produce an image. In plain X-ray imaging, the film directly absorbs penetrated X-rays. In CAT scanning, an electronic device called a "detector array" absorbs the penetrated X-rays, measures the X-ray amount, and transmits the data to a computer system. A sophisticated computer system, in turn, calculates and analyzes data from each detector in each level, and finally reconstructs multiple, two-dimensional, cross-sectional images.

HOW DOES IT WORKS?

DETECTOR ARRAY

CLASSIFICATION

AbdominalBoneHead Vascular

The four classifications of the types of scans are:

Depending on the type of scan, you may not be allowed to eat/drink a few hours prior to scan.Wear comfortable clothing or a gown will be provided.All metal and electronic possessions that can be removed must be removed.Intravenous contrast (if necessary) is injected into patient.Patient is then asked to lay on the machine platform and aligned.

PROCEDURE INVOLVED

NAME SOURCE OF DATA

NAME SOURCE OF DATA

Atom probe tomography Atom probeConfocal tomography LaserElectrical capacitance tomography

Electron capacitance

Microwave tomography MicrowaveOptical coherence tomography InterferometryOcean acoustic tomography SonarZeeman Doppler imaging Zeeman effectOptical projection tomography Optical microscopeOptical diffusion tomography Absorption of light

TYPES OF TOMOGRAPHY

ADVANTAGESIt emits a series of narrow beams through the human body, producing more detail information than standard single beam X-rays.

These are able to distinguish tissues inside a solid organ.

It gives the detailed 3D images of various body parts.

It is used to illustrate organ tear and organ injury very quickly.

Iodine is the usual contrast dye. Some patients are allergic to iodine and may experience a reaction that may include nausea, breathing difficulty or other symptoms.The amount of radiation used during a CT procedure is considered minimal, therefore the risk for radiation exposure is very low.Radiation exposure during pregnancy may lead to birth defects.

RISKS ASSOCIATED

Cost is high.Restriction on number of exams in a given period of time.Women who are pregnant, generally are discouraged from having a CAT scan performed.Risk of getting cancer.Intravenous or oral contrast can be uncomfortable.Decrease the time needed for scan/Decrease the amount of radiation required for scan.

LIMITATIONS